1) Field of the Invention
The present invention relates generally to crop conveying ducts for harvesters, and, more specifically, to a conveying duct for a cotton harvester.
2) Related Art
Cotton harvesters such as the John Deere Model 7455 Cotton Stripper include a large central duct for conveying cotton upwardly and rearwardly from the stripping units toward a cleaning grate adjacent a cotton cleaner and a basket on the harvester. Several problems exist with the previously available ducts. The ducts, which are fabricated from relatively heavy sheet metal and require welding, are expensive to manufacture. Large flat surfaces on the duct are very prone to flexing or "oil canning" motion caused by turbulent air flow within the duct. The motion results in fatigue, particularly at joints which are spot-welded, and decreases duct reliability. To reduce such motion, additional structure is provided on a portion of the duct, increasing cost and weight.
The trajectory of the cotton is influenced by the duct configuration, and present duct configurations fail to provide good air flow and evenly distributed cotton flow across the width of the duct, thereby decreasing conveying, separation grate and cleaner efficiency. The cotton tends to concentrate in the central portion of the duct so that the effective cleaning area of the separation grates is reduced. The central concentration also results in bunching of material on the grate assembly eventually leading to plugging, usually when there is low air speed on one side of the assembly. On some grate assemblies, plates are provided at the sides of the grates in the areas where there are relative dead spaces. To distribute the centrally concentrated material across the width of the cleaner, vanes are added to the cleaner inlet area.